The top or proximal edge region of a graft prosthesis, particularly one used to exclude an abdominal aortic aneurysm (AAA) or an aneurysm within the thoracic arch, is that portion of the device which is perhaps most critical to clinical success. Typically, it is the portion of the graft that forms the critical seal against the walls of the aorta to prevent leakage of arterial blood directly into the aneurysmal sac (a situation known as a Type I endoleak). In the case of a stent graft that employs a suprarenal stent or other stent that extends beyond the top edge of the tubular graft, (e.g., the ZENITH® AAA Endovascular Graft, Cook Incorporated), the top edge region also represents the portion to which the stent is sewn or otherwise attached or secured to the graft fabric, typically with a series of sutures. For stent grafts placed in the aorta, the pulsatile forces of blood being exerted on the device are sufficiently great such that over time, the sutures may break or pull through the material, which can cause the anchoring stent and graft to separate. If this occurs, the device may migrate or shift, resulting in the aneurysm no longer being excluded and making a subsequent rupture of the aneurysm potentially lethal to the patient.
While endoleaks can occur anywhere where an aortic stent graft is placed, they can be particularly troublesome when the graft is placed to treat an aneurysm occurring in the region between the renal arteries and the iliac bifurcation. If the neck of the aneurysm (the healthy portion or the vessel between the aneursymal sac and renal arteries) is short or tortuous in shape, it may be difficult to get proper alignment, anchoring, or a good seal between the graft and the vessel wall, possibly resulting in a Type I endoleak in which the sac may continue to be pressurized with blood.
What is needed is an improved proximal edge region of the graft portion of a stent graft prosthesis or covered stent to help ensure secure anchoring of the supporting structure or stent(s) to the fabric or material, and secondly, to ensure a good seal with the vessel wall such that leakage of blood or fluids does not occur along the proximal edge of the prosthesis.